Gillian Pearce

The Use of Stock Orthoses to Assist Gait in Neuromuscular Disorders: A Pilot Study

This pilot study compares the effect on walking speed, in eight subjects with neuromuscular conditions, of wearing Ligaflex ankle-foot orthoses (AFO), Leafspring orthoses and shoes or with shoes alone. Range of motion, muscle strength and sensation were tested in the lower leg. Subjects underwent a standardized timed 10-m walking test five times in each of the orthoses and shoes as a measure of gait efficiency. A self-administered questionnaire was used to seek the subjects perceptions of their functional difficulties and their opinions about the relative comfort and stability of these orthoses. Subjects had reduced ranges and strength of dorsiflexion and eversion. Some had proprioceptive deficiencies. Mean walking speed was 0.99 m/s (Leafspring) and 1.1 m/s (Ligaflex or shoes) compared to about 1.3 m/s for a normal population. Repeated measures ANOVA revealed that subjects were significantly slower in Leafspring compared to Ligaflex or to shoes. Questionnaire results rated the Leafspring as least comfortable and the Ligaflex most stable. Providing stability may be more important than assisting foot clearance when weakness is restricted to distal muscles. Further research is required to evaluate the comfort and effectiveness of orthoses to compensate for ankle instability in people with neuromuscular conditions.

An Investigation of Fluid Flow through a Modified Design for the 'GP' Device

We present 3-D FLUENT simulation modelling of the GP’ Mechanical Thrombectomy Device (MTD) used with a modified funnel structure. Comparisons are made of the results obtained from this modelling with actual measurements made in an in-vitro model of the ‘GP’ MTD with an end mounted funnel structure used in experiments. There was good agreement between the theoretical modelling and the in-vitro measurements. Such a device (with its end mounted funnel structure) may be used to remove older blood clots in arteries. We conclude that the 3-D FLUENT modelling is useful in predicting the performance of such a funnelled device, prior to actual construction of the finalised design.

Comparison of the Effectiveness of Three Methods of Recanalization in a Model of the Middle Cerebral Artery: Thrombus Aspiration via a 4F Catheter, Thrombus Aspiration via the GP Thromboaspiration Device, and Mechanical Thrombectomy Using the Solitaire Thrombectomy Device

Introduction. This paper compares different approaches to recanalization in a model of the middle cerebral artery (MCA). Methods. An occlusive thrombus (lambs blood) was introduced into the MCA of a model of the cerebral circulation perfused with Hartmanns solution (80 pulsations/min, mean pressure 90u2009mmu2009Hg). Three methods of clot retrieval were tested: thrombus aspiration via a 4F catheter (n = 26), thrombus aspiration via the GP thrombus aspiration device (GPTAD) (n = 30), and mechanical thrombectomy via the Solitaire Device (n = 30). Results. Recanalization rate was similar for all 3 approaches (62%, 77%, and 85%). Time to recanalization was faster with aspiration devices (41 SD 42u2009s for 4F and 61 SD 21u2009s for GPTAD) than with the Solitaire (197 SD 64u2009s P < .05 Kruksal-Wallis). Clot fragmentation was the same in the Solitaire (23%) and the GPTAD (23%), but higher with the 4F (53%, P < .05). Conclusion. In this model, thrombus aspiration was faster than mechanical thrombectomy, and similarly effective at recanalization. These results should be confirmed in vivo.

Developing a technique to measure intra-limb coordination in gait : Applicable to children with cerebral palsy

Lower limb intra-limb coordination was investigated using sagittal plane kinematic data extracted from gait data recorded using a Vicon system (Vicon Motion Systems Ltd., Oxford, UK) of 20 normal (N) and 20 children with cerebral palsy (CP). Walking speed, maximum and minimum flexion and range of motion (ROM) were calculated. The repeatability of the data was checked by calculating the coefficient of multiple correlation. Data were also processed to determine angular velocity of hip and knee joints. A logical spreadsheet was devised to determine when both joints moved in the same direction (in-phase), in different directions (antiphase, AP) or if either joint was immobile (JS). In-phase joint motion was further subdivided into in-phase flexion (IPF) and in-phase extension (IPE), which comprises in-phase during stance phase (IPEst) and in-phase during swing phase (IPEsw). Data were processed using two threshold values for angular velocity below which the joint was considered to be immobile. The threshold values used were 0.05 degrees /% of gait cycle and 0.025 degrees /% of gait cycle. Children with cerebral palsy had reduced ROM and walked more slowly than normal children. There are significant differences between N and cerebral palsy coordination phases with marginally greater significance at the 0.05 degrees /% threshold for most component parameters; the exception being in-phase flexion. It is therefore suggested that this threshold value (0.05 degrees /%) is used for future work.

The “GP” Mechanical Thrombectomy Device

We present data concerning the extraction of clots using the newly invented GP mechanical thrombectomy device (MTD). Artificial and porcine clots of various lengths were used in plastic tube models of an artery. We investigate the pressures and times taken for clot extraction together with the volumes of fluid extracted. We also investigate the impact of using a funnel structure mounted on the end of the device, on clot removal times and fluid removed. Finally, we present results involving clot extraction from the posterior popliteal artery of a cadaver. Our data indicated that: The embedded GP MTD is the most effective device regarding artificial and porcine blood clot removal. This result is consistent with previous published data on this device. The GP MTD was effective in removing clots positioned in the posterior popliteal artery of a cadaver. The embedded GP device removes less fluid compared with the end-mounted GP device. This confirms previous studies. There appears to be a relationship between funnel angle and pressure. Lower extraction pressures are required for larger funnel angles mounted on the GP device. Shorter times of clot extraction are required for larger funnel angles.

Modelling of the "GP" Mechnical Thrombectomy Device MTD

Presented is a study involving (i) theoretical modelling of the newly invented ‘GP’ Mechanical Thrombectomy Device (MTD) and (ii) laboratory verification of the theoretical modelling. For the latter, the MTD was placed in two positions (i) end mounted on a classic Seldinger catheter and (ii) embedded within the Seldinger catheter. Blood clots from porcine arteries supported in an arterial jig assembly were extracted. The results indicated that clot removal volumes were less with the embedded device and supported the theoretical modelling findings in respect of pressures required to facilitate clot removal.

Modelling and simulation of a thrombectomy probe applied to the middle cerebral artery by using the bond graph technique

Thrombosis is produced by the formation of a clot inside blood vessels causing an abrupt interruption of the blood flow. In the cerebral arteries, this occlusion can take place due to the presence of a clot that has formed at another location of greater diameter. It then obstructs the cerebral artery due to its smaller cross section. The process concerning the removal of this obstruction involves catheterisation. The experimental probe under study in this paper was developed by Dr G. Pearce and Reverend Neil Perkinson [1]. The probe, which when developed further may form the basis of a new Thrombectomy Aspiration Device (TAD) is called the GPTAD. Once fully developed, the GPTAD may provide a means of clot removal from vessels in the human arterial system e.g. the cerebral vessels. The modelling that we present in this paper, taking into account the catheter, the probe, artery, blood clot and adhesion forces, may assist with the optimisation of the design of the GPTAD probe. In the model used for the simulation both mechanical and hydraulic aspects have been considered with the purpose of combining the effect of the fluid-blood transmission for the different sections of the vein and the catheter.

Simulation of the GPTAD Applied to the Removal of Blood Clots That Arise during Peripheral Vascular Disease

A number of Thrombectomy devices using a variety of methods have now been developed to facilitate clot removal. We present research involving one such experimental device recently developed in the UK, called a GP Thrombus-Aspiration-Device (GPTAD). This device has the potential to bring about the extraction of a thrombus. Although the device is at a relatively early stage of development, the results look encouraging. We present an analysis of modelling this device using modelling techniques. Such modelling appears to be highly effective in simulating the device under a variety of conditions with a view to assisting in the optimisation of the GPTAD. The aim of this simulation model is to obtain the minimum pressure necessary to extract the clot and to verify that, both the pressure and the time required to complete the clot extraction are reasonable for use in clinical situations, and are consistent with any experimentally obtained data.

Analysis and Simulation of the Adhesion Forces between Clot and the Artery Wall for a Novel Thrombectomy Device Applied to the Middle Cerebral Artery

A number of Thrombectomy devices using a variety of methods have now been developed to facilitate clot removal. We present research involving one such experimental device recently developed in the UK, called a GP Thrombus Aspiration Device (TAD). This device has the potential to improve the process of extracting thrombosis clots in the cerebral arteries. The development of a simulation model for this device is shown using Bond-Graph formalism applied to modeling and simulating the adhesion forces between the clot and the artery wall. Bond-Graph technique is a visual methodology that adds more transparency to the processes and it has turned out to be remarkably useful as it is a simple, effective method that can be applied to any physical system where there is a power exchange. Such modelling appears to be able to simulate the device under a variety of conditions which may assist in the optimisation of the ‘GP’ TAD device if the novel design features of the device can be effectively incorporated into the model.

A Versatile Low Cost Arterial Simulator

Numerous simulators have been developed for the training of surgeons concerning many surgical procedures. In many cases, the simulators are both demanding of space and are costly. We have designed a low cost versatile simulator that can be used almost anywhere on most computer systems.